Saute the onions with the olive oil for about 10 minutes in a medium-size pot at medium-low heat. Do not burn! Then, add the rice, sugar and salt, stir. Cover and cook at very low heat until the rice looks see-through. Add the nuts, currants, mint, dill and 1/2 cup water. Stir occasionally at low heat. Cook until all the water evaporates and put them aside.

In the meantime, clean the mussels, scraping with a knife. Half open the round part of the shells; and with a knife, cut out the beards. Stuff the empty half of the shells with the rice filling and close up. Place the shells in a large pot with 1/3 cup water. Place a small plate upside down over the shells (this is to prevent the shells from unfolding while being cooked). Simmer for 20-25 minutes until the water is absorbed.

Let it cool down first, brush with a little olive oil. Then, place them on a serving dish. Serve the Stuffed Mussels chilled or at room temperature with lemon wedges.